<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }

        body {
            background: #34495e;
        }

        main {
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
        }

        main .btn {
            display: block;
            height: 30px;
            width: 150px;
            border: solid 2px #e74c3c;
            background: none;
            color: white;
            position: relative;
            text-align: center;
            display: flex;
            justify-content: center;
            align-items: center;
            overflow: hidden;
            cursor: pointer;
            box-shadow: 0 3px 8px rgba(0, 0, 0, .3);
        }

        main .btn::before {
            transition: all .8s;
            /* align-self: center; */
            content: '';
            position: absolute;
            width: 0px;
            height: 100%;
            background: #e74c3c;
            z-index: -1;
            transform: skewX(-45deg);
        }

        main .btn:hover::before {
            width: 200%;
        }
    </style>
</head>

<body>
    <main>
        <a class="btn">
            HOUDUNREN
        </a>
    </main>
</body>

</html>